GREMI NON-THERMAL PLASMAS AND HYDROGEN PRODUCTION

Transcription

1 GREMI NON-THERMAL PLASMAS AND HYDROGEN PRODUCTION F. Ouni, E. El Ahmar, O. Aubry, C. Met, A. Khacef, and J. M. Cormier GREMI-Polytech'Orléans, 14 rue d'issoudun, B.P. 6744, Orléans Cedex 2, France

2 Introduction Considering the evolution of energy resources, the use of non thermal plasmas applied to hydrogen production could be developed in a significant way. Results obtained at GREMI Laboratory with different types of plasma devices are presented.

3 Outlines The following points are presented : (1) Methane steam reforming. (2) Ethanol steam reforming. (3) Carbon monoxide removal and hydrogen production. (4) Hydrogen fuel enrichment.

4 (1) Methane steam reforming Non thermal plasma at atmospheric pressure can be used for steam reforming CH 4 +H 2 O >3H 2 +CO Experiments clearly demonstrated the ability of blowing discharges to increase the conversion efficiency of chemical reactions at low temperature.

5 Methane steam reforming The plasma reactor consists of three anodes arranged around of a single cathode. Gas In Discharges are ignited at the outlet of injection tube and then pushed by the flow. Anodes Cathode Pyrex tube Gas Out

6 Methane steam reforming CH 4 +H 2 O Inlet Ceramic tube (Diameter 16mm) S Magnet Anodes N Voltage Va1 Voltage Va 2 Discharge Cathode (Diameter 6mm) 0V Outlet H 2, CO, CO 2.???

7 70 Methane steam reforming The following values present the best results obtained in our experimental conditions: methane conversion = 50% for M < 0.67 and a hydrogen production energy cost of 1-2 Wh/Nl of H 2 for M > Outlet H2 and CO concentrations with H2O - CH4 mixtures 60 % H2, CO H2 % CO % CH4 % CO2% M : methane/water molar ratio Power (W) Outlet H 2 and CO concentrations with H 2 O-CH 4 mixtures ( C 2 H 2, CO 2 <1%)

8 Methane steam reforming Conclusions and perspectives Syngas and hydrogen production is possible using a blow discharge with a corresponding energy cost of 1 to 2 Wh per litre of hydrogen. Further tests must to be performed, in order to improve the conversion and reduce the carbon monoxide concentration for fuel cells applications. Tests with propane and butane are underway.

9 (2) Ethanol steam reforming Ṭhe plasma reactor Gas outlet Current 155 ma RMS Graphite electrodes Electrical discharge Water/ethanol mixture 2mm Simple geometry Easy to realized

10 mole fraction. 1.0E E E E E E E E E E E+00 Ethanol steam reforming Dried gas phase composition H2 CO CO X C 2 H 5 OH / X H 2 O mole fraction 6.0E E E E E E E+00 CH4 C2H2 C2H4 C2H X C 2 H 5 OH / X H 2 O

11 Ethanol steam reforming Comparative results : plasma / catalytic reactors. This work Auprêtre et al. [1] Llorca et al. [5] Inlet ethanol/water ratio H CO CO CH We observe that plasma technology allows to achieve a good level of H 2 mole fraction in a great range of ethanol/water ratio comparing to the catalytic techniques.

12 Ethanol steam reforming Conclusion & perspectives Ethanol steam reforming by a non thermal plasma technique a promising technique Advantages / catalytic reactors Energetic cost Simplicity Drawbacks : The CO concentration is the main drawback because of concentrations higher than 10 ppm. This value is considered as a limit in order to avoid poisoning fuel cells.

13 (3) Carbon monoxide removal Plasma Water Gas Shift reaction PWGS To reduce carbon monoxide an important reaction can be used: the water gas shift reaction (WGS) which led to H 2 and CO 2 from CO and H 2 O. CO + H 2 O CO 2 + H 2 DH= -41kJ.mol-1 WGS reaction could be achieved using a Dielectric Barrier Discharges (DBD).

14 Carbon monoxide removalcoh2omassflowmetermassflowmetercontrolledevaporatormixerfurnace120 CAnalysisVoltagemultiplierDBDreactorBlumleinlineTungstenwireAluminiumfoilElectronicSwitchHighvoltagepowersupply

15 Carbon monoxide removal Influences of the inlet H2O mole fraction and the peak voltage pulse on: a) H 2 O and CO mole fractions, b) CO and H 2 O mole fractions H2O 5.5 kv CO 5.5 kv H2O 3.7 kv CO 3.7 kv H2 5.5 kv CO2 5.5 kv H2 3.7 kv CO2 3.7 kv mole fraction mole fraction inlet H 2 O mole fraction inlet H 2 O mole fraction Total flow gas = sccm at 120 C

16 Carbon monoxide removal conclusions and perspectives PWGS It s possible to realize the water gas shift reaction in a DBD reactor. This investigation permitted to obtain conversion rates of CO close to 35% for the highest inlet H 2 O mixtures studied. Perspectives : Improve the conversion and reduce the energy cost.

17 (4) Hydrogen fuel enrichment Objective : NOx, CO, CO2,UHC and particles matter reduction Air Fuel Plasma reactor Enrichment of fuel in hydrogen Engine

18 Hydrogen fuel enrichment. The sliding discharge Air + CH 4 Admission to the pipe Sliding discharge Air Electrodes

19 Hydrogen fuel enrichment Exhaust gas mole fraction CO CO2 H2 H2O Electrical power (W) (Total flow rate=41l/min-1, 19% CH4, 81% air)

20 Hydrogen fuel enrichment Effect of a plasma treatment on engine NOx production Exhaust NOx concentration (ppm) CH4 :12,5 l/mn CH4 : 16 l/mn CH4 :21,6l/mn Primary supplying voltage

21 General Conclusion Technical Scientific Industrial Transfer Methane SR - Conversion improvement - CO abatement Complementary modeling Complementary treatments or PWGS improvement Ethanol SR - Scaling - CO abatement Complementary modeling Complementary treatments or PWGS improvement PWGS -Scaling - Progress in Kinetics - Reduction of energy cost - Conversion improvement Fuel Enrichment Design and material Engineering modeling Ready for industrial transfer